Rear-end collisions can occur when advance-warning of a breakdown for example is not given by the vehicle ahead. Rear-end collisions are also caused by the poor visibility and closeness to the warning equipment of the broken-down vehicle, the vehicles following do not have sufficient time or distance to respond. As required by transportation authorities, after an accident, an advance-warning device must be used to warn the vehicles behind, at a distance of 100-250 meters. However, when a warning device is manually placed, safety of the placer can be at risk. Therefore, a warning device that can be self propelled would be beneficial.